Wafer electroplating apparatus and method

ABSTRACT

A wafer electroplating apparatus and method, comprising a wafer turning assembly, a vertical movement assembly, a wafer tilting assembly, and a frame. The wafer turning assembly has a turning shaft and a clasp for holding a wafer. The wafer tilting assembly has a tilting table being driven by a driving system, e.g. a cylinder, carrying an electroplating unit and wafer turning assembly. Thus the clasp holding a wafer and the electroplating unit are simultaneously inclined at preset angle against the horizontal plane, allowing for a large inclination angle. Therefore, gas bubbles generated during electroplating readily escape, and quality of electroplating is improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a wafer electroplating apparatusand method, particularly to a wafer electroplating apparatus and methodhaving a wafer-holding clasp and an electroplating unit that are mountedon a common tilting table, being simultaneously tilted, so that largertilting angle can be adjusted for and gas bubbles generated duringelectroplating escape readily.

[0003] 2. Description of Related Art

[0004] When performing conventional fountain-type electroplating of awafer, the wafer is rotated to ensure uniform electroplating. The maindifference to bath type electroplating is that a clasp holding the waferis not completely immersed in a bath, establishing dry contact.

[0005] In fountain-type electroplating, a wafer is laid onto aelectroplating tank. During the ensuing chemical reaction, gas bubblesare produced, which readily stick to a electroplating surface of thewafer, causing the chemical reaction locally to stop, so that incompleteelectroplating results. To avoid this shortcoming, the wafer isinclined, allowing gas bubbles to escape easily.

[0006] Inclining of the wafer is done by turning the clasp holding thewafer by an inclination angle, so that the wafer and a fixedelectroplating tank inclined against each other. This results in thewafer, e.g. a 12 inch wafer, having an increased inclined diameter andthe clasp being immersed in the eletroplating solntion at an edgethereof. To avoid contamination of the clasp at a rear side thereof, theinclination angle is only chosen to be 1-2 degrees. However, a smallinclination angle results in insufficient clearing of gas bubbles. Onthe other hand, when being turned, the clasp is partially exposed insuccession to air and electroplating solution of the tank, which easilyleads to external air bubbles entering the electroplating solution inthe tank and impairing the chemical reaction, so that electroplating isdefective.

[0007] Fountain-type electroplating requires a suitable gap between thewafer and the top of tank. Thus pressure of the electroplatong solutionin the tank is maintained while liquid flows out through theelectroplating tank, so that liquid completely and uniformly covers thewafer. For maintaining pressure of the electroplating solution, thecross-section area of the gap is required to be smaller than thecross-section area of an inlet of the tank, resulting in an outflowvelocity of liquid that is larger than an inflow velocity thereof and inuniform flow through the gap.

[0008] While fountain-type electroplating allows for electroplating withuniform thickness, pockets of imperfect electroplating occur easily dueto gas bubbles. In order to allow gas bubbles readily to escape, thewafer is inclined. This not only creates an external disturbance, butalso due to an inclined orientation of the wafer and buoyancy leads tothe gas bubble movement.

[0009] In conventional art, the electroplating tank is fixed, only thewafer is inclined against a horizontal plane. Since the cross-sectionarea of the gap between the wafer and the tank is nonuniform, pressureis not maintained easily, the clasp is in turns exposed to air andliquid, resulting in external air bubbles enturing to the tank thatadversely affect the chemical reaction. Furthermore, inclination of thewafer is restricted to 1-2 degrees, as described in U.S. Pat. No.6,080,291, resulting in ineffective clearing of gas bubbles.

[0010] Moreover, the apparatuses disclosed in U.S. Pat. No. 6,080,291and No. 6,334,937 have the following shortcomings:

[0011] 1. When the wafer is inclined, with the tank unmoving, not onlythe cross-section area between the wafer and the tank nonuniform, butalso the permissible inclination angle is reduced.

[0012] 2. The clasp has no liquid blocking ring. When being held, thewafer at the rear side thereof is easily contaminated.

[0013] 3. Using a robot to incline the wafer requires a higher cost.

[0014] 4. No sealing device for the electroplating area is provided, soleaking of gas generated in the bath is not effectively prevented.

SUMMARY OF THE INVENTION

[0015] The main object of the present invention is to provide a waferelectroplating apparatus which allows to set large inclination angle, sothat gas bubbles escape easily, and which comprises a wafer turningassembly, a vertical movement assembly, a wafer tilting assembly, and aframe, with the wafer turning assembly having a clasp and a turningshaft and the wafer tilting assembly having an electroplating unit seton a tilting table driven by a driving system, e.g., a gas pressurecylinder, so that a mounted wafer and the electroplating unit aresimultaneously inclined at any preset angle.

[0016] Another object of the present invention is to provide a waferelectroplating apparatus which avoids contamination of the mounted waferat a rear side thereof by adding a protective ring to the clasp forkeeping liquid of an electroplating tank from reaching the rear side ofthe wafer.

[0017] A further object of the present invention is to provide a waferelectroplating apparatus which prevents gas from leaking to the outsidewhen the wafer is tilted by having a dome set on the wafer turningassembly, keeping the wafer turning assembly sealed during verticalmovements thereof.

[0018] A further object of the present invention is to provide a waferelectroplating method in which the wafer turning assembly with the claspand the electroplating unit, set on the tilting table driven by thedriving system, are simultaneously tilted, so that adjusting a mountedwafer at larger inclination angle against the horizontal plane ispossible, allowing gas bubbles generated during electroplating easily toescape.

[0019] The present invention can be more fully understood by referenceto the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a perspective view of the wafer electroplating apparatusof the present invention.

[0021]FIG. 2 is a front view of the wafer electroplating apparatus ofthe present invention.

[0022]FIG. 3 is a side view from the right of the wafer electroplatingapparatus of the present invention.

[0023]FIG. 4 is a top view of the wafer electroplating apparatus of thepresent invention.

[0024]FIG. 5 is a sectional view of the wafer electroplating apparatusof the present invention.

[0025]FIG. 6 is an enlarged sectional view of the clasp of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As shown in FIGS. 1-4, the wafer electroplating apparatus of thepresent invention mainly comprises: a frame 10; a wafer turning assembly20; a vertical movement assembly 30; and a wafer tilting assembly 40.

[0027] The frame 10 has a main body for stable mounting of othercomponents and four lower corners to each of which a wheel 111 and anadjustable support 112 are attached, allowing either to move or to fixthe frame 10. The frame 10 carries a pipe unit and a control unit.

[0028] The wafer turning assembly 20 has a casing 21. Inside the casing21, the wafer turning assembly 20 further has a gas inlet 22, a turningshaft 23, electrical connectors 24 and a driving unit 241. A motor and aconveyor belt in the driving unit 241 drive a rotating movement of theturning shaft 23. On a lower end of the wafer turning assembly 20, aclasp 25 is provided for holding a wafer, being in turn connected with agas pressure cylinder 26 inside the turning shaft 23. A dome 27 is seton the casing 21, covering the casing 21 tightly during electroplatingprocess and preventing gas from leaking to the outside as well as airentering the inside of the casing 21.

[0029] The vertical movement assembly 30 has a vertical column 31 set ona tilting table 42. A movement unit 32 with ball bearings and aservomotor 33 drive a vertical movement of the wafer turning assembly20, as in conventional art.

[0030] The wafer tilting assembly 40 is mounted on the main body 11,having a horizontal shaft 411 held in two seats 41 on two opposite sidesof the main body 11. The tilting table 42 is inserted between the seats41, turning with the horizontal shaft 411, with a lock 412 on the seat41 fixing the tilting table 42 a tilting angle. A connecting rod 421hingedly connects the tilting table 42 with a gas pressure rod of a gaspressure cylinder 43. The gas pressure cylinder 43 has a fixed endconnected with the main body 11. The tilting table 42 carries anelectroplating tank unit 44. The electroplating tank unit 44 contains anelectroplating solution and has an electroplating tank 441 serving as ananode. The electroplating tank 441 has a overflow tank 442, collectingliquid overflowing from the electroplating tank 441. The overflow tank442 is covered by the dome 27.

[0031] The gas pressure cylinder 43, via the gas pressure rod thereof,drives the tilting movement of the tilting table 42 towards a suitabletilting angle. Since the electroplating tank 441 and the clasp 25participate simultaneously in the tilting movement, the gap remainunchanged. Thus adjusting for a large tilting angle is possible,allowing the bubble generated during electroplating of the wafer easilyto escape, improving quality of electroplating.

[0032] Referring to FIG. 6, the clasp 25 has an upper part 251 and alower part 252 effectively holding the wafer. An cathode 253 is placedin a suitable position, and a liquid blocking ring 254 is laid around aperiphery of the clasp, preventing the electroplating solution fromcontaminating the wafer at a rear side thereof when a tilting angle isassumed.

[0033] The wafer electroplating method of the present inventioncomprises simultaneous tilting of the turning shaft 23 with the clasp 25and the electroplating unit, set on the tilting table 42 that isconnected with the horizontal connecting rod 411 and driven by a drivingsystem (in the embodiment shown, the gas pressure cylinder 43). Thusadjusting a mounted wafer at larger inclination angle against thehorizontal plane is possible, allowing the bubbles generated duringelectroplating easily to escape.

[0034] For better understanding, the steps of the wafer electroplatingmethod of the present invention are given as follows:

[0035] A. Inserting the wafer into the clasp; B. holding the wafer inthe clasp; C. lowering into the location of electroplating; D. incliningof the tilting table to incline the wafer; E. slowly turning the waferand electroplating; F. completing of electroplating; G. raising from thelocation of electroplating; H. reversing inclination of the tiltingtable; I. fast turning of the wafer for drying; J. stopping of thewafer; K. opening the clasp; L. removing the wafer.

[0036] As the above explanation shows, the present invention offers thefollowing advantages:

[0037] (1) A large tilting angle (over 45 degrees) is possible, allowingthe gas bubbles generated during electroplating readily to escape.

[0038] (2) The tilting angle is freely adjustable, increasingflexibility.

[0039] (3) The clasp is not in turns exposed to air and liquid, so thatno gas bubbles hindering chemical reactions enter the electroplatingtank.

[0040] (4) Different designs of the clasp for larger wafer are notrequired, simplifying the assembly.

[0041] (5) Electroplating is performed in an unchanging electric field,any variation of the tilting angle does not alter the geometry ofcathode, anode and the wafer.

[0042] The wafer electroplating apparatus and method of the presentinvention provides for a wafer-holding clasp and an electroplating unitthat are mounted on a common tilting table, being simultaneously tilted,so that larger tilting angle is adjustable for and gas bubbles generatedduring electroplating escape readily. Thus an improved electroplatingapparatus and method are provided, providing for various practicalfunctions.

[0043] While the invention has been described with reference topreferred embodiments thereof, it is to be understood that modificationsor variations may be easily made without departing from the spirit ofthis invention which is defined by the appended claims.

1. A wafer electroplating method, comprising the steps of: A. insertinga wafer into a clasp; B. holding said wafer in said clasp; C. loweringsaid wafer to a location of electroplating; D. inclining of a tiltingtable to incline said wafer; E. slowly turning said wafer andelectroplating; F. completing of electroplating; G. raising said waferfrom said location of electroplating; H. reversing inclination of saidtilting table; I. fast turning of said wafer for drying; J. stopping ofsaid wafer; K. opening said clasp; and L. removing said wafer.
 2. Awafer electroplating apparatus, comprising: a frame, having a main body,on which a piping system and a control unit are installed; a waferturning assembly, having a casing and a lower end, to which a clasp forholding a wafer is attached; a vertical movement assembly, mounted on aside of said wafer turning assembly, having a vertical column, on whicha vertical driving device is installed, driving said wafer turningdevice in a vertical movement; and a wafer tilting assembly, having twoseats, which are fastened on two opposite sides of said main body, witha tilting table inserted between and held by said two seats, saidtilting table being inclined at a tilting angle, as driven by a drivingsystem via a connecting rod, said tilting table carrying said verticalshifting assembly and an electroplating unit; wherein a suitable valueof said tilting angle is set using said driving system, with said claspand said electroplating unit being simultaneously tilted and, by tiltingto any angles, the clearance between the two is kept constant, therebynot hindering fluid patent be changed. The tilting angle of the wafercan be tilted to a larger angles. Gas bubbles generated duringelectroplating of said wafer is readily to escape from surface.
 3. Thewafer electroplating apparatus according to claim 2, wherein said waferturning assembly further comprises a gas inlet, a turning shaft,electrical connectors and a driving unit, with a gas pressure cylinderbeing installed inside said turning shaft, holding said clasp.
 4. Thewafer electroplating apparatus according to claim 2, wherein said clasphas a cathode at a suitable position and a liquid blocking ring.